During the last three years it has been demonstrated that safe and highly effective RV-based vaccines can be constructed and further emphasize their potential utility as efficacious anti-HIV vaccines. Recent research results indicate that even previous promising HIV-1 vaccine approaches, which prevented an AIDS-like disease in rhesus macaques, failed due to CTL escape mutants. We hypothesize that successful HIV-1 vaccines need strong humoral and cellular immune responses and our preliminary data indicate that such responses can be induced by RV-based HIV vaccines. This grant proposal is directed towards the further detailed analysis of the immunogenicity of RV-based HIV-1 vaccines and the improvement of their immunogenicity. After detailed studies utilizing different methods in a mouse model, promising approaches will be further analyzed in nonhuman primates. In Aim 1 we propose to analyze RV vectors expressing multiple genes such as HIV-1/SIV GagPol and HIV-1 Env and compare their immunogenicity to vaccines expressing single HIV-1/SIV proteins. Aim 2 analyzes the potency of the co-expression of cytokines or a pro-inflammatory molecule to enhance the immunogenicity of RV-based vaccine. Aim 3 is directed toward an efficacy study of the RV-based HIV-1 vaccines in the rhesus macaque model system. Thus, we will pursue several complementary approaches designed to further improve our HIV-1 vaccines, study their anti-HIV directed immunogenicity in detail, and test their efficacy in the rhesus macaque model system.